How to use Python 3.6.8?

I have AWS Lambda. It run without problem with Python 3.6.8. But when Serverless or AWS Lambda updated to Python 3.6.9 (without any change to my code), it won’t pass anymore. There comes following error: “/usr/bin/python3.6: No module named pip”

What should I do to use exactly Python 3.6.8? I can find only “Python3.6” from serverless.yml etc.

I have already tried to update to Python 3.7, 3.8, and 3.9 but then there comes other problems and I can’t build&deploy it. That is the reason why I first want it to run again with Python 3.6.8, and then try to update to newer version of Python.